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Re: [Moderator Action] Defaults

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 30 Nov 2000 11:50:51 +0000
To: "J C Theriot" <jim.theriot@posc.org>
Cc: <xmlschema-dev@w3.org>
Message-ID: <f5b4s0p65lw.fsf@cogsci.ed.ac.uk>
"J C Theriot" <jim.theriot@posc.org> writes:

> What does 'default' mean in the context of processing a document defined by
> an XML Schema?
> 
> In the context of DTD, the meaning of default is well defined:  the result
> of correctly parsing an XML document using the DTD is an 'augmented'
> Information Set, with default values from the DTD supplied wherever the
> attribute is missing in the XML file.
> 
> The augmentations intended for the result of XML Schema processing seem to
> consist only of information items describing the status of the validation.
> If an element has a content type and a default is defined for it, is the
> missing value to be filled in by a 'next generation' XML parser?  Or are
> element-content defaults specified in the schema intended to be instructions
> to the application to impute a value for content missing in the Information
> Set?

Not sure what aspect of the spec. failed to make this clear, but
defaults work for XML Schema processors exactly parallel to the way
they work for DOCTYPE processors:  they augment the infoset.  For
instance, the description of the Attribute Default Value [1] and
Element Default Value [2] Schema Information Set Contributions make
clear that after schema processing, the Infoset is augmented with
defaults where needed.

ht

[1] http://www.w3.org/TR/xmlschema-1/#sic-attrDefault
[2] http://www.w3.org/TR/xmlschema-1/#sic-eltDefault
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Thursday, 30 November 2000 06:51:08 GMT

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